Method for cleaning gas filter bags

Claim 1

In a method of exhausting gas from a bag filter compartment into an exhaust passage of a filter unit, wherein a solids laden gas is passed from a primary source through filter bags located in the bag filter compartment and the resultant filtered gas is exhausted through the exhaust passage which is controllable by valve means, and wherein the valve means is periodically moved to close the exhaust passage and a cleaning gas is passed from a secondary source through said bags countercurrent to the flow of the solids laden gas and at an elevated pressure with respect to said solids laden gas, after which the valve means is moved to open the exhaust passage and the flow of cleaning gas is terminated, the improvement comprising the steps of: moving a first portion of said valve means from said exhaust passage to fully open only a restricted passageway between said compartment and said exhaust passage to allow a first predetermined relatively restricted flow of gas through said restricted passageway from said compartment to said exhaust passage and thereafter moving a second portion of said valve means from said exhaust passage to fully open said exhaust passage to allow a relatively unrestricted second predetermined flow of gas from said compartment to said exhaust passage.